Genomic analysis has shown that Australia’s invasive rabbit population likely originated from a shipment of two dozen wild English rabbits that arrived near Melbourne on Christmas Day 1859. The study also reveals that the wild ancestry of the herd probably gave him an edge over previous arrivals. .
Rabbits have invaded most of the Australian mainland and have had a disastrous impact on ecosystems, threatening some 300 species of plants and animals and causing hundreds of millions of dollars in damage to the agricultural industry each year. “This single event triggered this huge disaster, ecological and economic, in Australia,” says Francis Jiggins, an evolutionary geneticist at the University of Cambridge, UK, and co-author of the study.
breed like rabbits
Historical records suggest that the first European rabbits (Oryctolagus cuniculus) in Australia arrived in Sydney in 1788, with the first colonizers. Ships carrying rabbits continued to dock along the coast for decades, but it was not until the second half of the 19th century that the population grew significantly, spreading across the country at the rate of 100 kilometers per year.
Historical records also suggest that the rabbit expansion followed a shipment of animals that arrived for a certain Thomas Austin at Barwon Park, southwest of what is now Melbourne. His brother had trapped them around their family property in Baltonsborough, South West England.
Joel Alves, an evolutionary geneticist at the University of Oxford, UK, and his colleagues wanted to know if the genomic data supported the recordings. They analyzed the genetic data of 179 wild rabbits captured in Australia and New Zealand, France and the United Kingdom, as well as 8 domestic rabbits of different breeds.
They found that most mainland Australian rabbits were genetically similar, with mixed wild and domestic ancestry. The Australian rabbits also shared rarer alleles with rabbits from South West England than with those from elsewhere in the UK, suggesting they originated in Baltonsborough. By looking specifically at mitochondrial DNA, inherited from the mother, the researchers concluded that most mainland Australian rabbits are descended from around five females, introduced from Europe.
The researchers also found that the genetic diversity of rabbits decreased as animals were captured from Barwon Park, and that rare or absent alleles in wild rabbits increased. The researchers say these patterns are consistent with the idea that most rabbits in Australia originated in Barwon Park. The team reports its findings in the Proceedings of the National Academy of Sciences August 221.
“This is a very exciting article on a very important and well-researched topic,” says Martin Nuñez, who studies ecological invasions at the University of Houston in Texas. Using genetics to understand how unwanted animal invasions begin can help predict future invasions, he says.
Overall, the team says the rabbits’ wild ancestry was a big factor in triggering their invasion of the continent. “Wild rabbits are different,” says Alves. They exhibit traits such as fleeing stressful environments and digging burrows, which means they were likely better at escaping predators and surviving in harsh terrain than house rabbits, he says. Historical records suggest that Austin requested feral rabbits, and previous arrivals were largely domestic breeds.
The expansion of Australian pastoral lands and the widespread suppression of predators at this time would also have contributed to their expansion. “It was like a perfect storm,” says Alves. “You have the right rabbits in the right place at the right time, with the right changes in the environment.”
“The genetic analyzes seem very strong,” says rabbit geneticist Amy Iannella, a consultant based in Adelaide, Australia. She adds that although the country’s rabbit populations likely originated in Barwon Park, their rapid expansion may have been helped by people transporting the animals to other parts of the country, where they also began to spread. Rabbits are generally common animals that depend on shelter to survive and juveniles rarely travel more than a kilometre, she says. “The idea that rabbits are moving fast enough on the invasion front to colonize Australia so quickly from a single release, well, that seems extreme to me, given what we know of the rabbit ecology.